Conventional mobile stations in wireless networks include a radio frequency integrated circuit (RFIC), along with at least one modem that communicates with the RFIC. Some mobile stations have a multi-standard RFIC that may communicate with multiple modems, each assigned to a different air interface standard. For mobile stations of this type, it is possible that multiple modems may request write and/or read access from the RFIC at the same time. Thus, the RFIC usually provides some type of access arbitration in order to handle these requests.
Typical access arbitration techniques include a first in/first out (FIFO) method, a round robin method, and different priorities assigned to different ports. For FIFO implementations, access requests are granted in the order in which they are received. For round robin, each port may be given access once during each of a plurality of continuously repeated cycles. For priority-assigned ports, access requests are granted based on a pre-assigned priority for the requesting port. Thus, a high-priority port is always given access prior to a low-priority port.
However, these methods may result in a port having to wait too long for a response in some circumstances. For example, after a read request, the RFIC must respond within a specified period of time during which the requesting modem expects the read response. If the RFIC fails to respond within this specified period of time, an invalid read may occur. Thus, using FIFO or round robin may result in invalid reads due to a requesting port having to wait in line behind ports with lower priority requests. Using assigned priorities does not solve this problem, either, as a higher priority port may starve out a lower priority port, which can result in invalid reads for the lower priority port. Therefore, there is a need in the art for an improved method of providing access-based arbitration when multiple modems are requesting access to a single RFIC in a mobile station.